Marcel Desailly believes Rafael Leao must become "ruthless" and "forge his character" following comparisons between the Milan winger and Thierry Henry.

Leao, directly involved in 10 of the Rossoneri's 29 Serie A goals this season (scoring six and assisting four), opened his Portugal tally in their World Cup win over Ghana on Thursday.

Desailly won the Champions League and two Scudetti during his five-year stint at Milan between 1993 and 1998 - the same year he was a team-mate of Henry's in France's first World Cup triumph.

When asked if he thought Leao was similar to Henry, whose national record tally of 51 goals was equalled by Olivier Giroud in Les Bleus' victory over Australia on Tuesday, the former defender told La Gazzetta dello Sport: "Calm down.

"It seems to me that Leao became a star before he even became a star. He has enormous potential, but he doesn't give me the idea of being ruthless. I ask Leao to forge his character."

Meanwhile, Desailly praised another Milan player in compatriot Theo Hernandez, who appeared as a substitute in France's 4-1 triumph over the Socceroos and could remain at full-back for the remainder of the World Cup following injury to his brother Lucas.

"Theo Hernandez can become the strongest in the world," he added. "He is a chameleon, he has the ability to change his function within the team."

Having regained the Serie A crown last season, Stefano Pioli's side are eight points adrift of leaders Napoli after the opening 15 matches in the Italian top flight.

The Partenopei are unbeaten so far in their quest for a first Scudetto since the 1989-90 season, but Desailly does not believe they will maintain their momentum throughout the campaign.

"I love Napoli’s energy," he said. "But I doubt they can hold on psychologically until the end. They don't have the squad to hold up."